The present invention relates to a device for reducing the danger of accidental detonation of a land mine and, more particularly, to a shoe for working safely in a minefield and to a method of manufacture thereof.
Land mines are usually detonated when a weight, exceeding a predetermined threshold, is applied thereon. The sensitivity to the detonation of a mine is governed, on the one hand, by the desire to provide a mine that will explode under the application of a minimal weight and, on the other hand, a mine that will not be accidentally detonated by small animals passing by, wind-blown debris, etc.
Similar to the snowshoe, which enables a wearer to walk on deep snow without sinking, it has been suggested to use a minefield shoe composed of a flat, rigid surface lined with a thick rubber or plastic foam, which, as it is understood, reduces the weight per unit area of the wearer on the ground. The main disadvantages, however, of such a minefield shoe are the difficulty of movement or walking due to the rigidity of the relatively large surface required for contacting the ground, and, of even greater importance, the fact that such shoes are effective only on smooth ground. On uneven ground or on ground having scattered stones, the weight of the wearer is no longer evenly distributed across the entire tread surface but is concentrated on the highest and limited points of contact between the ground and the contact surface of the shoe. Moreover, the rubber or plastic foam is rapidly worn down, requiring frequent replacement. Hence, this type of minefield shoe is not sufficiently safe and is of limited usefulness.
U.S. Pat. No. 4,611,411 to Ringler, et al., teaches a minefield shoe that displays improved performance in terms of ground contact. The minefield shoe disclosed contains an inflatable, multiple compartment air cushion. In contradistinction to the snowshoe-type minefield shoe, when the ground contacting surface of the air cushion presses against an uneven terrain or against a protrusion, a portion or portions of the surface move inwardly, the extent of which depends, inter alia, on the air pressure prevailing inside the compartment. Since the outer skin of the compartments is deformable and the interior of the compartments are in fluid communication with each other, the increased internal pressure caused by the decrease in volume will quickly be xe2x80x9cabsorbedxe2x80x9d by all compartments, thus effectively allowing the deformation of the ground contacting surface so as to form a matching counterpart of the terrain. This, in turn, assures that the load on the shoe will, in most cases, still be evenly distributed along the entire ground contacting surface of the air cushion.
The compartments making up the cushion fluidly communicate with each other through external tubing having numerous three-way tube junctions (T-type or Y-type fittings). The external placement of the tubes and the accompanying fittings render the minefield shoe vulnerable to failures associated with deflation. Inadvertent and catastrophic deflation can occur when such a tube is accidentally snagged by a foreign object, such that the tube is separated from a fitting, or such that the tube is punctured or torn (e.g., by a sharp object on the ground or by excessive wear. A tube blowout or a seal failure may also occur as a result of an overly-high internal pressure, e.g., from over-inflation.
Perhaps the greatest disadvantage of the minefield shoe taught by U.S. Pat. No. 4,611,411 to Ringler, et al., is the susceptibility of the gas cushion to puncturing. Since the compartments of the cushion are designed to be fluidly communicable, in order to provide improved ground contacting and weight distribution, and failure within any one of the compartments (or tubes and fittings) results in substantially immediate and catastrophic deflation of the entire cushion, thereby nullifying the detonation risk-reducing properties of the shoe, and unexpectedly subjecting the user to various kinds of life-threatening dangers.
There is therefore a recognized need for, and it would be highly advantageous to have, a minefield shoe that achieves superior ground contact, like that of U.S. Pat. No. 4,611,411, but is highly robust and reliable. It would be of specific advantage for such a minefield shoe to have lower susceptibility to being punctured and to maintain satisfactory function even after being punctured. It would be of further advantage for such a minefield shoe to exhibit improved performance, in terms of weight distribution, even relative to the minefield shoe taught by the above-referenced application. Finally, it would be of further advantage for such a minefield shoe to be simple to manufacture, lightweight, compact, and easy to store and to inflate.
According to the teachings of the present invention there is provided a minefield shoe for reducing the danger of accidental detonation of a land mine by a wearer of the shoe, including: (a) a cushion including a plurality of inflatable compartments, the cushion having, when inflated, at least one flexible, substantially flat, ground-contacting surface extending across the compartments; (b) passages, disposed within the cushion, for providing fluid communication between the compartments, and (c) means for attaching the shoe to a boot of the wearer, wherein each of the compartments is in fluid communication with at least one other compartment, via the passages, so as to prevent any significant increase in internal pressure of any one of the compartments resulting from a decrease in internal volume of another compartment, thereby to allow deformation of the ground-contacting surface to form a matching counterpart of terrain engaged by the shoe, while maintaining a substantially even distribution of the load on the shoe along all of the ground-contacting surface.
According to further features in preferred embodiments of the invention described below, the passages include a tubular fitting.
According to still further features in preferred embodiments of the invention described below, the passages include a fitting having a substantially rectangular external profile.
According to still further features in preferred embodiments of the invention described below, the cushion includes at least one additional inflatable compartment that is fluidly isolated from and disposed above the plurality of inflatable compartments.
According to still further features in preferred embodiments of the invention described below, the additional compartment is a plurality of top compartments, each of the top compartments being in communication with at least one other top compartment.
According to still further features in preferred embodiments of the invention described below, the top compartments have passages, disposed within the cushion, for effecting fluid communication between the compartments.
According to still further features in preferred embodiments of the invention described below, the minefield shoe further includes: (d) at least one rigid tread member attachable to an upper surface of the cushion for evenly distributing a load of the wearer along the cushion and across a top surface of the compartments.
According to another aspect of the present invention there is provided a minefield shoe for reducing the danger of accidental detonation of a land mine by a wearer of the shoe, including: (a) a cushion including: (i) an inflatable top compartment, and (ii) an inflatable bottom compartment, for providing the cushion, when inflated, with at least one flexible, substantially flat, ground-contacting surface, the top compartment being disposed substantially on top of the bottom compartment, the top compartment being fluidly sealed from the bottom compartment; (b) at least one rigid tread member attachable to an upper surface of the cushion for evenly distributing a load of the wearer along the cushion and across a top surface of the top compartment, and (c) means for attaching the shoe to a boot of the wearer, wherein even with the bottom compartment in a deflated state, the cushion maintains a substantially even distribution of the load on the shoe along all of the ground-contacting surface.
According to still further features in preferred embodiments of the invention described below, the inflatable bottom compartment is a plurality of compartments, each of the compartments being in communication with at least one other compartment.
According to still further features in preferred embodiments of the invention described below, the compartments have passageways, disposed within the cushion, for effecting fluid communication between the compartments.
According to still further features in preferred embodiments of the invention described below, the inflatable top compartment is a second plurality of compartments, each of the compartments being in communication with at least one other compartment in the second plurality of compartments.
According to still further features in preferred embodiments of the invention described below, the flexible, substantially flat, ground-contacting surface is bonded to a bottom surface of the bottom compartment to form an integral sheet.
According to still further features in preferred embodiments of the invention described below, the flexible, substantially flat, ground-contacting surface is loosely attached to a bottom surface of the bottom compartment.
According to still further features in preferred embodiments of the invention described below, the ground-contacting surface is designed and optimized solely for maximal flexibility.
According to another aspect of the present invention there is provided a method for producing an inflatable minefield shoe for maintaining an evenly-distributed load on terrain, including the steps of: (a) providing at least two sheets, each sheet including a fabric layer and an impermeable coating adhering thereto; (b) fixing the sheets in a substantially parallel and substantially contacting disposition; (c) bonding the sheets in a series of pre-determined locations, so as to form a plurality of pockets, each of the pockets being in fluid communication with at least one other pocket, wherein the plurality of pockets, upon inflation, enables a ground-contacting surface of the minefield shoe to maintain a substantially even distribution of the load along the ground-contacting surface.
According to further features in preferred embodiments of the invention described below, the bonding is effected by means of high-frequency welding and an electrode.
According to still further features in preferred embodiments of the invention described below, the bonding is effected by means of heat-sealing.
According to still further features in preferred embodiments of the invention described below, the pockets are in fluid communication via passageways disposed within the plurality of pockets.
According to still further features in preferred embodiments of the invention described below, the passageways are formed by temporary insertion of a strip between the sheets, at predetermined locations.
According to still further features in preferred embodiments of the invention described below, each of the passageways is formed by disposing a tubular element between the sheets.
According to still further features in preferred embodiments of the invention described below, the tubular element is bonded to the sheets prior to step (c).